A projecting apparatus is widely used in our daily lives to project texts/pictures or image data onto a projection screen in order to facilitate the user to view the enlarged texts/pictures or image data in a visually comfortable manner. Recently, the general trends in designing electronic devices are toward small size, light weightiness and easy portability to meet the requirements of humanization. Correspondingly, the projecting system is developed toward miniaturization. As a consequence, the projecting system can be applied to electronic devices such as 3G mobile phones or personal digital assistants (PDAs). In addition, a small-sized projecting apparatus becomes a portable electronic device. On account of its portability, the user may use the small-sized projecting apparatus to watch movies everywhere they are, and thus the amusement purpose can be achieved without difficulty.
FIG. 1 is a schematic view illustrating a first conventional projecting apparatus. As shown in FIG. 1, the projecting apparatus 2A comprises a light-emitting unit 21a, a display element 22a and an optical lens module 23. The display element 22a is arranged between the light-emitting unit 21a and the optical lens module 23. For example, the display element 22a is a transmissive LCD element. The light-emitting unit 21a provides a visible light beam 25 to the display element 22a. Moreover, the visible light beam 25 provided by the light-emitting unit 21a illuminates an image shown on the display element 22a. After the visible light beam 25 from the display element 22a is transmitted through the optical lens module 23 and then outputted, the image is projected on a projection surface 9.
FIG. 2 is a schematic view illustrating a second conventional projecting apparatus. As shown in FIG. 2, the projecting apparatus 2B comprises a light-emitting unit 21b, a polarization beam splitter (PBS) 24b, a display element 22b and an optical lens module 23. The polarization beam splitter 24b is arranged between the display element 22b, the light-emitting unit 21b and the optical lens module 23. For example, the display element 22b is a reflective LCOS (liquid crystal on silicon) element. The light-emitting unit 21b provides a visible light beam 25. After the visible light beam 25 is transmitted through the polarization beam splitter 24b, the visible light beam 25 is directed to the display element 22b. Moreover, the visible light beam 25 provided by the light-emitting unit 21a illuminates an image shown on the display element 22b. After the visible light beam 25 from the display element 22b is sequentially transmitted through the polarization beam splitter 24b and the optical lens module 23 and then outputted, the image is projected on a projection surface 9.
FIG. 3 is a schematic view illustrating a third conventional projecting apparatus. As shown in FIG. 3, the projecting apparatus 2C comprises a light-emitting unit 21c, a total internal reflection (TIR) prism 24c, a display element 22c and an optical lens module 23. The total internal reflection prism 24c is arranged between the display element 22c, the light-emitting unit 21c and the optical lens module 23. For example, the display element 22c is a digital micromirror device (DMD). The light-emitting unit 21c provides a visible light beam 25. After the visible light beam 25 is transmitted through the total internal reflection prism 24c, the visible light beam 25 is directed to the display element 22c. Moreover, the visible light beam 25 provided by the light-emitting unit 21c illuminates an image shown on the display element 22c. After the visible light beam 25 from the display element 22c is sequentially transmitted through the total internal reflection prism 24c and the optical lens module 23 and then outputted, the image is projected on a projection surface 9.
FIG. 4 is a schematic view illustrating the optical lens module of the conventional projection apparatus. The optical lens module 23 may be applied to the projection apparatuses of FIGS. 1-3. As shown in FIG. 4, the optical lens module 23 comprises an optical lens group 231. The optical lens group 231 comprises plural optical lenses, which are sequentially arranged along an optical axis 2311 in the direction from an object side to an image side. By the optical lens group 231, the travelling direction of the visible light beam 25 from the display element 22 is changed. Consequently, the image shown on the display element 22 is enlarged and projected in a specified direction.
Moreover, as the demands on the quality of life are gradually increased, the people's appeals for image development are changed from the conventional 2D planar image and 3D planar image to the current 3D stereoscopic image. The appeal lies in the reality of watching the image. Consequently, the viewer feels that he (or she) is personally on the scene while watching the image. However, since the conventional projection apparatus is equipped with a single optical lens group, it is difficult to project out the realistic 3D stereoscopic image. In other words, it is difficult to use the conventional projection apparatus to achieve the 3D auto-stereoscopic efficacy.
As the entertainment and convenience needs are gradually increased, more users desire to interact with the image which is projected out by the projection apparatus. For meeting these needs, the manufacturers have to install an additional device at the outside of the conventional projection apparatus. For example, the additional device is a sensing device for sensing the human's behaviors in order to comply with the users' requirements. The additional device may increase the volume of the overall system. In other words, the arrangement of the additional device is detrimental to the miniaturization of the projection apparatus.
As mentioned above, the conventional projection apparatus and the optical lens module thereof need to be further improved.